Other Contributor(s):
Two projects are described in this report: Participatory Organic Potato Production and An Organic Fertilizer Calculator. Involved in the first were: Alexandra Stone, Horticulture; Lane Selman, research associate, Horticulture; John McQueen, faculty research assistant, Horticulture. In the second, are: Nick Andrews, Metro Area Small Farms Extension Agent, Horticulture, North Willamette Research and Extension Center; John Luna, Horticulture, campus; and Craig Cogger, WSU-Puyallup.

Extension program began: 2006

Description: Switch to abstract
Organic farms generally supply large amounts of organic matter to the soil through composts and cover cropping. Over time, these additions increase the size of the active pool of soil organic matter. These "rich" soils generally hold a great deal of nitrogen, but for the N to become available to the plants, it must be converted to available forms (ammonium-nitrogen and nitrate-nitrogen). In fact, a soil with 3 percent organic matter in the top foot contains about 5,000 lbs. of N per acre, but often only a small percentage has been released in a plant-available form through the mineralization process. This poses a problem for farmers: On the one hand. if sufficient N has been mineralized, then applying more readily available N (e.g., in chicken litter or fish meal,) would unnecessarily add to costs of production, and extra N could leach or run off to water sources. On the other hand, if not enough N has been mineralized, yields would suffer. The problem is that it's difficult to measure when and how much to apply (or not to apply) so that sufficient N can be delivered with precision to the plants while growing.

So far, one aspect of this work has been completed, Participatory Organic Potato Production; a second; An Organic Fertilizer Calculator is ongoing.

Participatory Organic Potato Production:
Through 2007, this project worked with a group of participating organic potato farmers on improving N management of their potato crop. (This group that became known as OSPUD, after its website www.ospud.com.) The project increased knowledge of best methods for N monitoring, developed typical system values that can be used in planning crop N budgets and in modeling of the N cycle for organic potato crops. Findings will assist growers in reducing their use of expensive, rapidly-available N inputs and will lower the amount of soil nitrate-N left over to leach to groundwater at the end of the growing season.

For the OSPUD project’s recommended methods for N monitoring, i.e., good ways to determine the amount of N available to the organic potato crop, please see “additional information,” where typical system values for use in planning crop N budgets and in modeling the N cycle for organic potato crops in western Oregon soils are also reported.

An Organic Cover Crop, Plant Available Nitrogen, Calculator:
Cover cropping is widely used in organic systems, but the plant-available N (PAN) benefit of cover cropping is difficult to assess on a field-by-field basis. Growers have identified better decision-making tools for cover cropping and nitrogen management as among their top research needs. An ongoing OSU project with organic growers is identifying farmer-friendly methods for assessing total aboveground N uptake by a cover crop. This project will take the next step, estimating PAN per acre from a cover crop (total N • the fraction of total N converted to PAN).

The goal is to develop a Cover Crop Calculator that can be used by growers and agricultural professionals to estimate the PAN amount and its dollar value. Objectives to address this goal are to (1) collect field and laboratory data on PAN release from 40+ cover crop treatments and (2) develop a regression model (Calculator) to estimate cover crop PAN.

Cover crop samples will be collected from established field experiments, and, in the lab, N release from cover crops in-soil incubations will be measured. A strong relationship is expected between cover crop total N concentration and PAN release. As validation of the lab incubation approach, in-field PAN release will be compared with in-lab PAN. Also, interaction with an advisory group within eOrganic* will be sought.
* eOrganic is a link from the OSU eExtension web site.

It Is anticipated that PAN release from cover crops will increase linearly as a function of crop N concentration, following a relationship similar to that observed in previous research with manures and organic fertilizers. This relationship will be incorporated into an Excel-based tool (Calculator) that can be used to estimate the dollar cost of cover crop nitrogen. The Calculator will be distributed by OSU Extension (via website) and eOrganic.

The Calculator should improve economic decisions by organic growers, while better estimates of cover crop PAN will also help growers meet their environmental protection goals, including reduced nitrate leaching to groundwater and reduced soil P buildup (by replacing manure with cover crops to supply N). Based on experience with downloads of the existing Organic Fertilizer Calculator, this Cover Crop Calculator is expected to be downloaded over 1,000 times during a year.

The information for this Extension program was last updated on: 10/28/2008

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Project Profile, ranking of the Extension program on a scale of -3 to +3. A blank means that category is not applicable in this case.